Wireless Keyboard Not Charging

Thank you both for your responses to my query. Yes, that is what the backup plan was if all else failed - use the USB phone charger. I am beyond embarrassed to relate that I had the L - R orientation of the ports reversed. The only excuse I can think of is that I was doing the cabling blind by feel since the wiring of the Mac Mini was such that I couldn't look at the ports directly. So instead of a USB port, the cable was plugged into the Ethernet port! Having said that, in retrospect I am surprised by how nicely, by feel anyway, the plug went into the back of the Mac Mini Ethernet port. It felt like a good solid connection!

A couple of observations following the correct insertion of the cable. Although it's hard to see owing to the small battery icon size, once the keyboard is charging, you do see the familiar lightning bolts - ⚡️⚡️ - inside the icon so at least you know it's charging.

Even though it is charging, the original 16% charge readout does not change as the charging progresses. It is only when you disconnect the cable that the reading is updated. OK so there is a complete accounting of my misadventures with the magic keyboard charging process. My whole setup is new and I've not had to charge the keyboard before if that is any excuse. Thanks again for your help.